Unsaturated aldehydes such as acrolein, methacrolein, cinnamaldehyde and atropaldehyde, unsaturated acids such as acrylic acid, methacrylic acid, cinnamic acid, .alpha.-phenyl acrylic acid, and the like are highly desirable compounds having particular use as specialty industrial chemicals and as monomers and comonomers in a variety of commerical polymers. Unsaturated nitriles such as acrylonitrile, methacrylonitrile, cinnamonitrile, atroponitrile and the like are similarly useful chemicals used in the manufacture of fabrics, insecticides, herbicides and plastics. The aforementioned unsaturated compounds are usually manufactured from monoolefinically unsaturated compounds such as propylene, isobutylene isoamylene, .alpha.-methyl styrene, .beta.-methyl styrene and the like which are considerably more expensive raw materials than more readily availably saturated and substituted saturated hydrocarbons. To date, commercial manufacture of the desired unsaturated compounds has been most successfully achieved by the vapor phase oxidation or ammoxidation of an olefin or an olefinically unsaturated alkyl aromatic.
Much time has been spent on various methods of converting the cheaper saturated compounds into the desired more valuable unsaturated nitriles, aldehydes and acids in a single step catalytic reaction. Particularly noteworthy is the fact that considerable effort has been expended to effect the desired oxidation of saturated hydrocarbons without breaking off one or more carbon atoms. This effort has met with a conspicuous lack of success and served to focus on the gap in this technology. The instant invention aims to fill that gap.
U.S. Pat. No. 3,365,482 teaches a process for the ammoxidation of saturated hydrocarbons and as background, lists a number of references which teach the ammoxidation of olefinically unsaturated hydrocarbons. Also included is a summary of the difficulties inherent in a process for the ammoxidation of saturated hydrocarbons, which difficulties no one will gainsay.
In U.S. Pat. No. 3,293,290 a process is disclosed for the manufacture of unsaturated aldehydes and acids from either paraffins or monoolefins in which a gaseous mixture of hydrocarbons and oxygen is catalytically converted into the desired products in the presence of hydrogen bromide or hydrogen iodide as a promoter. Table 1 (on page 3, column 5 of '290) indicates that overall percent conversion of propylene feed is about the same whether or not hydrogen bromide is used, and in fact whether or not any promoter is used.
The inappropriateness of hydrogen chloride as a promoter since it gave less unsaturated products than no promoter at all, is emphasized in the very first two tests of '290; to distinguish this reference from the instant invention right at the outset, pertinent figures for conversion of propylene to desired unsaturated products are reproduced from said reference under the heading Desirability of Chloride Promoter in the Examples section of the instant application on pages 10 and 11.
Another halide-promoted catalytic reaction is the subject of U.S. Pat. No. 3,293,292 wherein liquid normal butane is converted to acetic acid in the presence of a cobalt salt which is soluble in the liquid medium in which the oxidation reaction takes place. It will be noted that, unlike the reactions disclosed in U.S. Pat. No. 3,293,290 and the instant invention, the liquid phase reaction involves converting a lower alkane to the saturated acid rather than the unsaturated acids and aldehydes.
In the instant invention, applicants have discovered that saturated hydrocarbons and substituted saturated hydrocarbons having from 3 to 12 carbon atoms per molecule, and preferably from 3 to 9 carbon atoms per molecule, may be readily oxidized or ammoxidized by the instant vapor phase catalytic reaction utilizing an antimony-containing oxidation catalyst provided that a minor quantity of an inorganic or organic halide, a halogen or a halogen acid, as specified hereinafter, is incorporated with the feed. Fluorine and compounds of fluorine are excluded from the scope of the instant invention.